Mobile terminal devices such as smartphones and mobile phones can access the Internet via a wide-area wireless network (wireless WAN) provided by a telecommunications carrier. A certain type of mobile terminal device functions as a router with an access point function for a wireless WAN to allow another mobile terminal device to access the Internet. Such a communication function of the mobile terminal device is called a tethering function.
Use of the tethering function allows a mobile terminal device unable to connect to the wireless WAN to access the Internet in a location where there is no wireless LAN access point. In tethering, any one of plural mobile terminal devices operates as a master device to connect to the wireless WAN, and any other one or more mobile terminal devices operate as slave devices to connect to the wireless WAN using a relay function of the master device. For the connection between the master device and each slave device, communication standards such as wireless LAN, USB, and Bluetooth (registered trademark, which is abbreviated as BLT below) are known.
Patent Document 1 discloses a communication system that reduces power consumption when a communication terminal device having a tethering function operates as a master device. This document describes that a degree of congestion on a WLAN channel through which tethering communication is performed is acquired from an information providing device installed in a facility so that the master device will switch the channel to another. Patent Document 2 discloses a program configured to reduce the power consumption of a relay terminal to save a battery when tethering is established between the relay terminal functioning as a wireless router, such as a smartphone or a mobile phone, and client terminal such as a laptop PC or a tablet terminal.
This document describes that the relay terminal or the client terminal switches the tethering communication to either a high-speed wireless communication system with high-power consumption such as WiFi (registered trademark) or a low-speed wireless communication system with low-power consumption such as BLT depending on the communication speed or the communication traffic. Patent Document 3 discloses a mobile terminal that selects a tethering terminal appropriate for a user from among plural tethering terminals. This document describes that status information on the remaining battery level and whether the battery is on charge, the network contract details, and the like are acquired from tethering terminals to select an appropriate tethering terminal.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2013-219740
[Patent Document 2] Japanese Patent Application Laid-Open No. 2014-107783
[Patent Document 3] Japanese Patent Application Laid-Open No. 2012-227610